Fully-closed-loop servomotor control system
First Claim
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1. A fully-closed-loop servomotor control method comprising steps of:
- adding the difference between a move command and an actual position of a servomotor to a value in a first error counter at every predetermined processing period;
adding the difference between the move command and an actual position of a machine moving part driven by means of the servomotor to a value in a second error counter at every said processing period;
obtaining the difference between the respective output values of the first and second error counters and smoothing the difference to obtain an error counter difference;
obtaining a speed command by multiplying the sum of the error counter difference and the first position deviation by a predetermined position loop gain;
delivering the difference between the speed command and the actual speed of the servomotor to a speed control loop; and
additionally applying a predetermined correction value for backlash correction to the input of the first error counter when the rotating direction of the servomotor is reversed.
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Abstract
A first integrated position deviation between a move command and an actual position of a servomotor and a second integrated position deviation between the move command and an actual position of a machine moving part are obtained, the difference between the first and second integrated position deviations is smoothed, and a modified move command is created by adding the smoothed difference to the first integrated position deviation and is delivered to a speed loop. When the reversal of rotation of the servomotor is detected, a backlash correction value is added to the first integrated position deviation to update it.
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Citations
5 Claims
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1. A fully-closed-loop servomotor control method comprising steps of:
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adding the difference between a move command and an actual position of a servomotor to a value in a first error counter at every predetermined processing period; adding the difference between the move command and an actual position of a machine moving part driven by means of the servomotor to a value in a second error counter at every said processing period; obtaining the difference between the respective output values of the first and second error counters and smoothing the difference to obtain an error counter difference; obtaining a speed command by multiplying the sum of the error counter difference and the first position deviation by a predetermined position loop gain; delivering the difference between the speed command and the actual speed of the servomotor to a speed control loop; and additionally applying a predetermined correction value for backlash correction to the input of the first error counter when the rotating direction of the servomotor is reversed. - View Dependent Claims (2, 3, 4)
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5. A fully-closed-loop NC servo system comprising:
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a first error counter which receives a move command from a numerical control device, a feedback value for the position of a servomotor, and a predetermined move command correction value for backlash correction, to obtain a computation result by subtracting the feedback value for the position of the servomotor from the sum of the move command and the move command correction value, and accumulates the computation result for outputting; a second error counter which receives the move command and a feedback value for the position of a machine moving part driven by means of the servomotor, to obtain a computation result by subtracting the feedback value for the position of the machine moving part from the move command, and accumulates the computation result for outputting; error counter difference computing means which receives the respective output values of the first and second error counters, to obtain a computation result by subtracting the output value of the second error counter from the output value of the first error counter, and carries out smoothing processings for the computation result for outputting; adder means which receives the respective outputs of the first error counter and the error counter difference computing means to obtain the sum of the two outputs, and delivers the obtained sum to a speed control loop; and backlash correcting means which determines whether or not the sign of the move command is inverted and changes the predetermined move command correction value for backlash correction from zero to a predetermined value in accordance with the backlash between the servomotor and the machine moving part, when an inversion of the sign is detected.
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Specification